Pilot-operated proportional pressure control valves are disclosed in the prior art, for example, by US 2008/0017261 A1. They are used, for example, in mobile machinery for electrodynamic actuation of clutches. In the actuation of these clutches, a critical requirement is that the valves in the off state must produce a pressure of exactly zero bar (0 bar), so that the assigned clutch can reliably disengage. However, the valves that meet this requirement have a certain serious disadvantage. The pilot oil flow that flows unused to the drain port is extremely large. Often the pilot oil flow reaches one liter per minute (1 l/min). The pilot oil also drains unused to the drain port in the neutral position of the valve. In technical terms, the unused drainage of pilot oil is also referred to as leakage.
In complex gear applications in which a large number of these valves is often needed, the energy loss, which can be in the kilowatt range in the extreme case, is considerable.
This leakage is even more serious in applications in which the clutch valves are supplied using a hydraulic accumulator. The high leakage then necessitates frequent recharging of the hydraulic accumulator.